Pre-initiation complex
The pre-initiation complex (PIK) is a protein complex in the nucleus of eukaryotes . Its assembly is a prerequisite for the beginning of transcription of most genes . The individual components of the complex ensure the exact positioning at the beginning of the gene and thus prevent reading errors. The pre-initiation complex consists of the core promoter of the gene, the transcription factors TFIIA , TFIIB , TFIID , TFIIE , TFIIF , TFIIH and the RNA polymerase II . After reading six bases, it is separated in promoter: TFIIA: TFIID and TFIIB: TFIIE: TFIIF: TFIIH: pol II, the latter moving further on the DNA.
The individual steps in the assembly of the complex are binding of TFIID to the promoter, binding of TFIIA and TFIIB to it, binding of pol II via TFIIF, then TFIIE and finally TFIIH. The DNA is bent 80 degrees by TBP / TFIID, which later brings it close to the polymerase. The helicase activity of XBP / TFIIH ultimately leads to an opening of the DNA double strand. This concludes the pre-initiation phase of the transcription.
When the complex is formed, the DNA template is brought up to the catalytic center of the RNA polymerase (RPB1 / RPB2). This facilitates the formation of the first phosphodiester bond, with which transcription begins. As a result, the TFIIB subunit separates from the pre-initiation complex. At this point in time, the open configuration can still change to the closed configuration if, for example, there is no ATP supply to the TFIIH or if there are inhibiting factors.
Individual evidence
- ↑ Reinberg / reactome: RNA Polymerase II Transcription Pre-Initiation ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
- ^ Kornberg RD: The molecular basis of eukaryotic transcription . In: Proc. Natl. Acad. Sci. USA . 104, No. 32, 2007, pp. 12955-61. doi : 10.1073 / pnas.0704138104 . PMID 17670940 .
- ↑ Timmers / reactome: RNA Polymerase II Transcription Initiation ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
Web links
- Illustrations / schemes of the pre-initiation complex
- bmb.psu.edu ( Memento from December 17, 2008 in the Internet Archive )
- imcb.osaka-u.ac.jp ( Memento from March 9, 2012 in the Internet Archive )
- biochem.ucl.ac.uk